Mesocosm: A Recognized Alternative for Environmental Effects Monitoring, 2002 Environmental Conference Proceedings

D. A. McCabe, J. Bagnall and L. Greco

The Canadian federal environmental effects monitoring (EEM) program was developed to aid in assessing the adequacy of both the Pulp and Paper Effluent Regulations and the Metal Mining Effluent Regulations of the federal Fisheries Act. These programs have been designed to achieve national uniformity in monitoring of effects while considering site-specific factors. Key components of each EEM program include liquid plume delineation and monitoring of fish, and benthic invertebrates and supporting environmental parameters (e.g., effluent and water chemistry, sublethal toxicity testing and sediment chemistry) in reference and exposed areas. This assessment is normally conducted using field survey techniques, as they are the most environmentally relevant approach for effects assessment.

However, there may be situations where field surveys do not provide the required information. These situations could include confounded receiving environments (areas where two or more industries discharge to the same location) and unsafe sampling conditions. If standard EEM field surveys cannot be conducted, use of scientifically defensible, cost-effective, and technically feasible alternative monitoring methods can be considered.

Artificial stream systems or mesocosms are recommended as scientifically defensible monitoring alternatives for EEM programs. Mesocosms are large-scale bioassay units that are towed to or near industrial sites for a realistic simulation of actual conditions when standard EEM in-field monitoring is not possible. A number of EEM studies have been undertaken to study the effects of the liquid effluent discharged from pulp and paper mills and metal mines. This paper will present a general review of recent mesocosm applications, the design of two different mesocosm units, and several case studies on projects in which mesocosms were used.